The subject matter of the present disclosure broadly relates to the art of vehicle suspension systems and, more particularly, to a rigid jounce bumper that is capable of providing substantially rigid support of axially-applied loads and also capable of lateral deflection under laterally-applied loads. A gas spring assembly including such a rigid jounce bumper is also disclosed.
Wheeled motor vehicles of most types and kinds include a sprung mass, such as a body or chassis, for example, and an unsprung mass, such as two or more axles or other wheel-engaging members, for example, with a suspension system disposed therebetween. Typically, a suspension system will include a plurality of spring devices as well as a plurality of damping devices that together permit the sprung and unsprung masses of the vehicle to move in a somewhat controlled manner relative to one another. Movement of the sprung and unsprung masses toward one another is normally referred to in the art as jounce motion while movement of the sprung and unsprung masses away from one another is commonly referred to in the art as rebound motion.
Generally, the range of motion of a suspension system extends between a first or fully compressed condition and a second or fully extended condition. To eliminate contact between opposing portions of the sprung and unsprung masses, contact between opposing portions of components of the suspension system or contact between any combination thereof, jounce bumpers are commonly installed on one or more portions of the vehicle to prevent such opposing portions from directly impacting one another. Thus, during jounce motion of the suspension system, an opposing component will contact the jounce bumper rather than impacting the component on or near which the jounce bumper is mounted.
Jounce bumpers of a variety of types, kinds and configurations have been developed and are commonly used. Though the size and shape of jounce bumpers vary widely, known jounce bumpers can generally be grouped into two categories, namely, compliant jounce bumpers and rigid jounce bumpers. The former are commonly formed from materials capable of relatively high deflections under load, and are often formed from rubber or elastomeric foam compounds.
Generally, compliant jounce bumpers act to cushion or otherwise soften the impact that would otherwise be associated with a sudden movement toward a full jounce condition. As such, compliant jounce bumpers are well suited for use in relatively light duty applications, such as use in the suspension systems of passenger vehicles and light trucks, for example, where ride comfort is a more significant factor. Additionally, the materials from which such compliant jounce bumpers are formed is normally capable of withstanding at least some amount of lateral deflection, such as would be due to a laterally-applied load, without undergoing permanent deformation or another undesirable alteration of its performance characteristics. Furthermore, suspension systems used in passenger and other light-duty applications typically permit a relatively small or otherwise reduced amount of lateral displacement, which is normally well within the capability of known compliant jounce bumpers to withstand.
Unfortunately, the elastomeric materials that result in compliant jounce bumpers being so well suited for high-comfort, light-duty applications have generally been found to be quite poorly suited for high-load and/or heavy-duty applications. One exemplary reason for such a lack of suitability for use in heavy-duty applications relates to the elastomeric nature of the material itself. More specifically, for a given compliant jounce bumper to have a suitable compressed height (i.e., a compressed height that will be sufficient to inhibit contact between opposing suspension components under a heavy load), the corresponding free height of such a given compliant jounce bumper would likely be great enough to adversely effect the overall travel or other performance characteristics of the suspension system. Said differently, the elastomeric material would have to compress so much to support the high-load condition that the unloaded height of the material could result in the compliant jounce bumper undesirably interfering with the performance of the suspension system or components thereof.
Other exemplary difficulties with the use of compliant jounce bumpers under high-load and/or heavy-duty conditions involve the performance of such compliant bumpers when contacted at relatively high angles. As has been previously mentioned, in order to support a substantial load at a given height, a compliant bumper must possess a taller free height due to its high level of axial strain. Many suspension geometries allow the mounting spring surfaces to articulate at an angle relative to one another, such as in a trailing arm-type suspension, for example. On such suspensions, a taller compliant jounce bumper would contact the opposing structural member much earlier in the suspension travel and at a greater angle. When contacted at a relatively high angle, such as an angle of about 10 degrees or more, for example, a compliant jounce bumper will deflect laterally. This can undesirably increase the possibility of interference with other components and can also undesirably reduces suspension travel. In contrast, a less compliant jounce bumper would be able to utilize a lower free height and would normally contact the opposing structural member at a later point during suspension travel. Thus, the structural member will typically contact a less-compliant jounce bumper at a lower angle which will thereby minimize the aforementioned issues with compliant jounce bumper. One further issue involves maintaining the attachment of such compliant jounce bumpers on a corresponding securement feature under such high levels of lateral displacement and contact angle.
Oppositely, rigid jounce bumpers are commonly formed from materials that deflect a relatively small amount under load, such as high strength and/or fiber reinforced plastic materials, for example. Rigid jounce bumpers are not normally considered to be well suited for use in light duty applications (e.g., passenger vehicle applications) because of the minimal deflection and corresponding ride harshness that is associated with the use of such jounce bumpers. However, rigid jounce bumpers are well suited for heavy duty applications, such as in truck, tractor-trailer and other over-the-road vehicle applications, for example, where it is desirable to provide a sacrificial component that can prevent impacts between more permanent and/or expensive components. Additionally, it is often desirable to lower trucks, trailers or other vehicle bodies onto the jounce bumpers to provide a solid foundation for loading and/or unloading of the vehicle body.
Unfortunately, known rigid jounce bumpers are not well suited for accommodating laterally-applied or side load conditions. One example of such a condition can occur when a rigid jounce bumper is axially compressed between opposing structural members and the structural members are then moved laterally relative to one another. Such an action is sometimes referred to in the art as a “scrub load” and can generate a shearing action on the rigid jounce bumper that can result in permanent deformation or other undesirable alterations in the jounce bumper due to the highly rigid (i.e., substantially non-elastomeric) nature of the material forming the same. Accordingly, it is believed desirable to develop a rigid jounce bumper that overcomes the foregoing and other disadvantages of known constructions.